OpenSSH announced that OpenSSH 6.2 and 6.3 are vulnerable to an authenticated code execution flaw. The vulnerability affects the AES-GCM cipher. As a quick fix, you can disable the cipher (see the URL below for details). Or you can upgrade to OpenSSH 6.4.
A user may bypass restrictions imposed to the users account by exploiting the flaw, but the user needs valid credentials to take advantage of the flaw.
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